Compact high-speed teleprinter mechanism

ABSTRACT

A compact code-controlled high-speed character printer uses a rotatable wheellike printing element of low inertia which is rotated by selective, digitally-metered movement of a tensioned cable to position the selected character for imprinting by the pressing together of the printing element and the impression paper between a relatively-movable rigid backup anvil and an impression hammer. The received codes position the printing element by the shifting of binary cable-guiding pulleys through the selective electromagnetic release of respective pulleycontrolling latches.

United States Patent [72] Inventor Frederick P. Willcox 565 Oenoke Ridge, New Canaan, Conn. ew [21] Appl. No. 744,606 [22] Filed June 21, 1968 [45] Patented Oct. 5, 1971 [54] COMPACT HIGH-SPEED TELEPRINTER MECHANISM 5 Claims, 7 Drawing Figs.

[52] 0.8. CI 197/49, 178/34, 197/18 [51] 1nt.Cl B41j1/22 [50] Field of Search 197/l8,48, 49, 50, 51, 52, 53, 54, 55; 178/34 [56] References Cited UNITED STATES PATENTS 410,629 9/1889 Arnold 197/49 438,430 10/1890 Clerk 197/49 X 638,092 11/1899 Carmonaw. 197/51 X 710,089 9/1902 Williams 197/49 1,533,207 4/1925 Pfannenstiekl 178/27 1,623,810 4/1927 Pfannenstiekl 178/34 2,236,663 4/1941 Adams 197/53 2,661,683 12/1953 Beattie 197/55 X 2,757,775 8/1956 Hickerson 197/49 Primary Examiner-Edgar S. Burr Attorney-Homer R. Montague ABSTRACT: A compact code-controlled high-speed character printer uses a rotatable wheellike printing element of low inertia which is rotated by selective, digitally-metered movement of a tensioned cable to position the selected character for imprinting by the pressing together of the printing element and the impression paper between a relativelymovable rigid backup anvil and an impression hammer. The received codes position the printing element by the shifting of binary cable-guiding pulleys through the selective electromagnetic release of respective pulley-controlling latches.

PATENTED [JCT 5L9?! SHEEI 1 BF 2 SERIAL AND PARALLEL INPUTS PARALLEL OUTPUTS +SUPPLY DELAY PRINT RESET YZKQ 5o TIMER TIMER TIMER K Z8: ,jj t 52 72 7'8 60a-- 606 A INVENTOR: F P. w/LLcox COMPACT HIGH-SPEED TELEPRINTER MECHANISM BACKGROUND OF THE INVENTION Commercially available character printers, especially those which are arranged for code control over wire or radio circuits, are costly, have limited printing speeds, and are of bulky size and shape. Regardless of type of imprinting elements employed, such as type bars, type wheels or drums, or the like, their speeds are severely limited by the masses and consequent inertias of the moving parts, the long printing strokes involved, and relatively high energy levels needed to effect adequate imprinting impacts. These characteristics, in turn, involve excessive forces, and consequently the necessity for "beefing up all parts of the equipment to withstand the shocks and vibration. A vicious circle of design limitations results, and as a result, no truly compact high speed printer has yet appeared. Moreover, no printer has been designed which will enable the overall configuration to be especially adapted to the space and power limitations of portable or multistation terminal applications.

SUMMARY OF THE INVENTION The mechanism according to the invention is especially adapted for producing the printed characters or words in a sequence along a single line, e.g., of tape or the like), but with only slight additional complexity, it may also be employed as the printing portion of a card or sheet printer. In either case, the small size, simplicity and low cost of the mechanism make it useful in many situations where known teleprinters cannot be employed. For example, in portable or mobile applications, or wherever a large number of stations are controlled from (and must control) a single information center, these characteristics are especially valuable.

The invention further aims to provide a printer mechanism whose size and arrangement are especially adapted for combination with a manual encoding keyboard in a compact and convenient flat-package format, for use where the printer is used both to receive and record code signals from remote points, as well as to make a record under local keyboard control, as in two-way communicating. The arrangement of the invention is such as to allow the just-imprinted medium (tape or sheet) to be immediately inspected by an operator as each character is printed; that is, the imprinted record medium is presented for immediate and continuous inspection of at least the last several word groups of a message, and the position of the exposed record medium is along the major face of the keyboard for direct view by the operator.

A further object of the invention is to provide a printer employing a rotatable character font element, such as a simple wheel, in which the extremely light and low-inertia construction of the front element contributes in several novel ways to the special objects of the invention. Thus, the character imprint is obtained by the impacting of the record medium against the printing surface of the type face, the latter being closely adjacent the tape on one side thereof and directly backed up by a rigid and, usually, massive anvil surface, and the hammer or impression means moving toward and away from the other side of the tape. The reverse arrangement is not precluded; that is, one in which the anvil and the font element together perform the slight motion needed for imprinting. The type element can thus be very light and thin, and the lightness of the element operates to reduce its moment of inertie, and this enables it to be rotated with relatively low power to effect character selections at high speeds, and by relatively simple control means. In essence, the element skims along adjacent the backup member from which it is spaced only an amount such as to provide clearance or absence of frictional drag. The impression paper (tape) is preferably of the pressure-printing type, but a marking ribbon may be employed within the scope of the invention. In the preferred form, maximum visibility of the characters, as printed, is provided by placing the type wheel behind the tape, and the hammer or impressing member above it. The type wheel may be slotted between character configurations to avoid distortion of the rim due to the peening action of repeated impressions.

The digital character-selecting drive of the font wheel is also a novel type, in which the wheel is rapidly rotated to a precise printing position for each received group of code signals, without excessive overshoot, by the special action of a set of electromagnetically controlled operators upon a flexible cable or the like wrapped about a disc or shaft connected to (or serving as) the font wheel hub. As will appear, these operators are arranged to have a differential effect upon the wheel rotation, some of them causing it to turn in one direction when energized, while another (or others) will cause it to turn oppositely. This arrangement greatly reduces the need for extreme rotations of the font wheel between character selections, thus reducing the power requirements and minimizing wheel overshoot, and it also permits the overlapping of certain essential time intervals required for machine operation, for increased rapidity of operation.

A further novel feature of the binary cable-differential font wheel drive of the invention lies in the use of at least some of the code-selected electromagnetic operators in a cable-releasing mode (as contrasted with a cable-pulling mode), and in the simultaneous resetting of all of the cable-path defining elements by a single operation of a single electromagnetic reset operator. Individual selecting magnets are required only to effect the release of latching elements (and not by their own power to rotate the font element), and these latching elements are thereafter restored by the single common reset operator. The operation of the latter element is also conveniently employed to effect a letter-space increment of relative motion of the paper message tape or other record medium, and to energize the printing or impressing mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS the invention will be described below in connection with a preferred embodiment thereof fully illustrating the application of the principles of the invention, the description having reference to the accompanying drawings, in which:

FIG. 1 is a plan view, partly broken away, of a complete tape printer and keyboard combination.

FIG. 2 is a schematic diagram, partly in block form, of the signal paths and circuits employed in the operation of the equipment.

FIG. 3 is a plan view, to a larger scale, of the characterselecting, imprinting, and resetting mechanisms of the printer of FIG. 1.

FIG. 3-A is a fragmentary face view of a modified form of the font wheel of FIG. 1.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 3.

FIG. 6 is schematic vertical section of an alternate form of imprinting mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 of the drawings shows in plan or top view a preferred arrangement of the printer when applied to printing a continuous line of characters along a narrow strip 10 of pressure-sensitive paper tape upon which a visible marking can be made by impacting the paper against a type face lying beneath the paper. The tape 10 is supplied from a roll of tape marked I2, which reel lies upon a circular turnable plate 14 journaled in the bottom plate 16 of the casing indicated as a whole by numeral 18. Since the tape is fed incrementally beneath the printing hammer as each character is imprinted, or is fed idly to provide a space between words, by mechanism to be described, it is desirable to provide a relatively free loop of tape from which the small amount fed for each character or space can be withdrawn quickly without the necessity for accelerating the entire tape roll 12. To this end, the tape leaving roll 12 is guided about a roller 20 journaled on the casing bottom plate 16, and thence about a loop-forming roller 22 pivoted at the outer end of an arm 24 pivoted on the bottom plate (beneath the turntable) as at 26. Arm 24 carries a friction-block 28 positioned thereon to jam tightly against the rim of turntable 14, in the position shown, when the spring 30 urges the arm 24 towards that position.

When an increment of the tape is fed in the direction of the arrows in FIG. 1 (by means to be described), this increment is supplied by a decrease in the loop length as arm 24 is pulled in the clockwise direction. When the arm 24 swings up, as tape is fed from the loop, the block 28 rises slightly away from the rim, releasing the braking effect, in preparation for restoration of the full loop as the arm returns downward. Reverse motion of the tape is prevented (as to the increment which has just been fed) by the ratchet employed in the incremental feeding drive, so that after the feeding step, spring 30 restores the arm 24 counterclockwise and thereby replaces the original loop length from the roll 12, turning it clockwise in a relatively leisurely manner and thus avoiding the necessity for its rapid acceleration. The brake block 28 damps any tendency for the roll 12 to overshoot, and the parts come to rest ready, with the brake reengaged, for a succeeding tape feed step after the printing of the selected character.

From roller 22, the tape is fed between guide posts 32 fixed to the casing bottom, which direct the tape onto a doubly curved tape guide plate 34 from which it emerges for further travel along the casing bottom 16 adjacent one inner longitudinal edge thereof, under a guide 36, and ultimately upward around a friction puck or tape feed roller (to be described) from which it travels back to the left (in FIG. 1) after being imprinted beneath the print hammer 38. The feed roller is positioned to the right of the centerline of the casing 18, so that a substantial length of the imprinted tape is made visible to the operator as the tape proceeds to the left in a tape guide channel 40, the tape lying between a lip forming one edge of this channel, and the inner wall surface of casing wall 42, and thence passing out of the casing via an exit slot in the left-hand casing wall 44.

The arrangement just described yields many advantages. The tape supply roll and its guide path are so positioned that a maximum of the space within the casing is made available for the supply roll, and consistent with the desired relatively thin or flat configuration of the casing. At the same time, a maximum amount or length of the imprinted tape is presented for view by one facing the keyboard of the device, whether the printing is being performed under control of signals received from a communication channel, or in response to operation of the keyboard at this terminal.

The top panel of the casing 18 is preferably provided by a thin, flat contact-making keyboard 46 which may for example be of the type described in US. Pat. No. 3,290,439 issued Dec. 6, 1966 and owned by the present inventor. This keyboard acts as a cover for the printer casing, being preferably hinged thereto for easy access, and it is of course cut away to provide a window through which the imprinted tape may be viewed, as already described. A transparent plate or pane 48 closes this opening.

The signal flow paths and typical control circuitry of the printer are diagrammed in F l6. 2 of the drawings, numeral 46 again designating the local keyboard thereof. The keyboard key operations control the supply of current from the supply line 50 via the delay timer 52 which is an electronic switch designed to trigger the printing hammer or other impression means) only after a sufficient time for selection to have been completed, and also to interrupt the keyboard supply momentarily after each key operation and to restore it when sufficient time has elapsed to ensure that double selection does not occur. The switch or timer 52 is supplied from the DC bus 54 connected through the on-off switch 56 to any suitable source, here indicated simply as a battery 58. When any keyboard key is depressed, current is supplied to a selected one or more of the output leads 60 of the keyboard, these being sufficient in number (six are shown as typical) to meet the binary coding requirements of the character and function-selecting choices provided. Additional output leads to provide for parity or other code-checking purposes may be provided. In the arrangement shown, lead 60:: is the 1-bit lead, 60b the 2-bit lead, 600 the 4-bit lead, 60d the 8-bit lead, 60e the 16-bit lead, and 60f the 32-bit lead. Each of these leads triggers a respective latch-magnet energizing circuit (of which only three are shown by way of illustration), here shown as comprising a normally nonconducting transistor 62e whose collector is connected to the positive-voltage bus as at 64, and whose emitter supplies current, when the cutoff bias provided by resistor 66 is overcome, to the typical latch magnet 68c to energize the same for a purpose to be described.

An optional connection is indicated by dotted lead 60g and a diode 65 therein, connected from lead 60c to the 8-bit transistor 62d at a point to the right of an isolating diode 67. This lead 60g is shown as open-circuited at X" for the regular 1, 2, 4, 8, l6 and 32-bit selection arrangement. When a smaller font wheel carrying a restricted font is employed, e.g., the 46-character font as shown, and that therefore does not require the total of 63 codes for character selection, it is preferred to use this alternate connection with a corresponding physical adjustment of the selecting mechanism (to be described below) so that the 16-bit selection (for example) may be replaced by a second 8-bit selection and also so that the 32-bit selection represents only 23 units of font travel. This results in a l, 2, 4, 8, 8, and modified-32-bit arrangement (46 character codes), and prevents possibly damaging overshoot of the font element, if a restricted font wheel were employed with full binary coding and if, by error, both an 8-bit and a 16-bit font drive action were to be performed during one character selection. This will be better understood after further description of the mechanism, given below.

The emitter of each transistor is also connected through a diode such as 68 to a conductor 70 to provide thereon a pulse (when any one or several of the transistors should conduct) to turn off the switch timer 52 for a predetermined interval, calculated to be sufficient to prevent the premature operation of a subsequent key from energizing any additional latch magnets than those operated by the preceding key action. The delay timer 52 thus prevents the superimposition of successive selection codes and consequent erroneous imprints, if the keyboard is operated at too rapid a cadence. The delay timer 52 also operates to provide a current pulse to the print timer 72 of sufficient duration to fully energize the print magnet 74 (which operates the printing hammer or impression means 38 to be described), via normally nonconducting transistor 76. A pulse derived, in turn, from the print timer 72, energizes the reset timer 78 which performs the same office for the reset magnet 80, via transistor 82, which includes in its collectorand-magnet circuit a parallel resistor capacitance circuit 84, (the capacitance value of 85 may be from 500 to 1000 microfarads) to provide a maximum pull-in current for the magnet, which current will then decrease to a suitable holding level established by the resistance value of the resistor 84.

The foregoing circuit arrangement is to be understood as given so that those skilled in the art will understand the operation of the printer mechanism to be described, and not for purposes of limiting the scope of the invention. Alternative circuits will be obvious to those familiar with such controls, in the light of the description given.

The physical construction of the printer mechanism itself is detailed in FIG. 3 of the drawings, which is oriented the same as in FIG. 1 but shows the right-hand portion thereof to a larger scale, and with the keyboard 46 removed to expose the underlying parts. Most of these parts are carried on the separate mechanism plate 86 lying upon the bottom of the main casing. The type (font) wheel is designated 88, journaled upon the plate 86 by a shaft to which it may be removably assembled as by a shoulder screw 89 (as in FIG. 3-A) for fontchanging purposes. The shaft also journals a cable drum 90 secured to the underside of the type wheel, or forming its hub, and about which drum is wrapped a flexible cable 92 secured to one end of a tension spring 94 whose other end is fixed to the plate 86 as by post 96. From drum 90, the other end of the cable 92 passes around a succession of pulleys 98, 100, 102, 104, 106 and 108 each freely rotatable near an end of one arm of a respective crank lever, these being numbered 110, 112, 11-3, 116, 118 and 120, and all being journaled upon suitable posts carried by plate 86. The extremity of cable 92 is anchored to a post 122 preferably rotatable in the plate 86 for precise adjustment of the total effective cable length between this post and the cable drum 90 that is afiixed to the type wheel 88. Since the cable is constantly under tension due to spring 94, this adjustment enables the angular position of the type wheel to be precisely set so as always to bring a selected printing character type face exactly into the proper printing position beneath hammer 38.

All of the five upper pulleys (98 through 106) are held in the position shown by reason of the engagement of the tails of their crank levers against the ends of respective stiff leafspring armatures such as indicated at 124e for the pulley 106. Since this particular armature, and associated parts, is typical of the others, only one needs to be described in detail. Thus, the armature l24e is mounted to plate 86 by a post 126, and its motion in the latching direction (shown) is limited by a stop post 128. When the magnet 68e (see FIG. 2) is energized, the spring armature is attracted and its and releases the tail of crank 118, allowing the tension in cable 92 to swing the crank counterclockwise to a limiting position defined by a stop 130 preferably fonned by the eccentric head of a screw or post frictionally held in plate 86, to allow for a fine adjustment of the extend of this rotation of the crank. A rounded nose 132 on the other end of the crank enters a cam notch 134 in one edge of a reset member 136, here shown as a slide urged downwardly by a spring 138 anchoredto the plate 86, and retained on the plate, and guided by, a pair of shoulder screws 140 passing through slots in the slide 136.

Before continuing the mechanical description, it is well to note that the raised characters or figures, constituting the entire font, will ordinarily extend around practically the entire periphery of the type wheel 88, and they may be arranged in any sequence to agree with the bit-coding scheme employed. In the system being described, the type wheel 88 is always returned, after one printing operation, to a zero or home position with a space symbol type face position aligned beneath hammer 38. It follows that the type wheel may rotate in either direction from this home position to effect the next character selection, and can position any selected character with no more than substantially 180 of rotation plus one character-space on the font wheel. This bidirectional selecting motion of the type wheel has important advantages, among which are the shorter selecting (type-face positioning) time required before the impression is made, and the reduction of overshooting of the type wheel and of the time required for the wheel to come to rest with the selected character in printing position.

Returning to FIG. 3, it will be seen that the amount of motion of each of the four cable pulleys- 98 through 104 is calibrated to agree with the bit value assigned to its respective release magnet, the latter being energized under control of the corresponding selecting conductors 60a through 60] of FIG. 2. That is, for example, the tail of crank 110 (for pulley 98) will engage the stop 142 after a very short travel of the crank, when magnet 68a (the 1-bit magnet) is energized. The crank 112 of pulley 100 will move substantially through twice this angle, and so on, the position of each stop for these four pulleys being adjusted (according to the full font arrangement) so that the travel of the corresponding pulley produces exactly double the amount of effective shortening of the cable path as does the next higher-placed pulley. Pulley 106, however, will be moved the same distance as pulley 104 (rather than twice that distance), and pulley 108 will be moved a distance corresponding to 23 angular units of font rotation.

Assuming for the moment that the lowermost pulley 108 is always latched in the position shown, the selective energization of the upper five magnets will allow the type wheel 88 to rotate, from its home position, any number of precisely equal angular units, from one unit angle (when only magnet 68a is energized) through a maximum number of units (when all the five magnets are energized). These rotations will all represent clockwise rotation of the type wheel, as operation of the magnets shortens the cable length from its anchored extremity (at 122) to the type wheel cable drum, and spring 94 is constantly urging the wheel clockwise. Energization of none of the magnets would leave the type wheel at. its home position.

To enable the type wheel to be rotated selectively through the additional angular positions corresponding to counterclockwise rotation of the type wheel from its zero position, the 32-bit magnet 68f will be energized (by a selecting pulse on lead 60f of FIG. 2), pulling its leaf spring armature [24f from beneath the tail of crank lever 120. A spring 144, which is stronger than spring 94, urges crank counterclockwise against its stop screw 146, causing pulley 108 to move to the left and to pull against the cable 92; the amount by which the effective cable length is lengthened being precisely in correspondence with the selected number of angular units assigned to the 32-bit magnet (23 units of angular movement in the example shown). Thus, the operation of magnet 68f determines which l80 half-sector of the type wheel is brought into use for printing, the angular rotation of the type wheel in either sector being precisely selected by the combination of magnets 680 through 68e which are energized. This differential arrangement, as already indicated, limits the maximum type wheel displacement to not more than half a turn plus (at the most) one character space on the font wheel.

For use with a limited-size font as shown in FIG. 3, with fewer characters on the wheel 88 (and as previously mentioned), excessive cable pulling'and overtravel of the print wheel would result if both the 8- and 16- bit drives happened to be actuated in error. This can be prevented by adopting the dual-8 binary series described above, the second 8-bit selection being obtained by the circuit there described, and by adjusting the stop of the 16-bit" crank lever 118 to provide the same travel distance as does the stop for the 8-bit crank 116.

Referring still to FIG. 3, the spring 94 is connected to cable 92 by the connecting piece 95, and a somewhat resilient stop bracket 97 secured to the baseplate has a hole which passes the cable 92. The cable length (to connection 95) is made such that, if only magnet 68f is actuated, to call for the maximum (one-half turn) excursion of the font wheel 88 in the counterclockwise direction, the piece 95 will be engaged against resilient stop bracket 97, thus setting a limit to wheel rotation (and the extension of spring 94). To perform the printing or impressing operation, a pot magnet 74 secured on plate 86 is energized (by circuit block 72 of FIG. 2), attracting its armature which is secured to a pivoted hammer arm 152 mounted on a rugged pivot structure 154, against the restoring force of a spring 156. The left end of the hammer arm carries the hammer element 38 (appearing also in FIG. 1), which strikes the tape 10 from above, against the selected type face on wheel 88, and producing the visible outline of the character. The font wheel, in this region, is closely backed up by the solid anvil surface provided, for example, by the upper surface of a block 190 secured to the mechanism plate 86. Wheel 88 has only minimum rotational clearance over the anvil. As will be described below, this block 190 also mounts parts related to the tape feeding function. In any event, the closely spaced solid backing for the font wheel enables an adequate impression force to be used, without substantial deflection of the wheel, and this is in turn compatible with the desirable lightweight construction of the latter for low inertia. Obviously, this solid backing element need not be absolutely fixed, so long as it performs its function properly at the time the printing impression is accomplished.

After each printing operation, it is necessary to reset (latch) all of the selecting cranks which were released during selection of the character just printed. To do this, the reset magnet 80 (also in FIG. 2) is energized, attracting its armature 158 which is attached'to ,one arm 160 of a crank lever pivoted on plate 86 at 162. The crank lever has a second arm 164, and in actuality, these crank levers are duplicated (FIG. lever arm 164 being above the other one marked 165, so as to straddle a lever 166 also pivoted on the post 162. The arm 164 and its lower counterpart 165 are connected by a pin 168 which in the position shown rests upon the upper edge of lever 166, and a hairpin spring 170 has one end abutted against a pin 172 on arm 160, thence winds about the pivot post 162 and passes downwardly past the lower edge of lever 166, as at 174, thence beneath the lower bell crank lever, around the pivot post 162, and finally has its end abutting a pin on the lower crank in a position just below pin 172.

Means are provided to brake the font wheel at its approximate home position at the time of reset, to prevent overtravel of the wheel. To this end, a bent braking lever 99 is pivoted at 101 to the baseplate to the left of the font wheel axle, and arranged for the interior edge of its median or elbow portion to engage and brake a portion of the periphery of the cable drum 90 of the font wheel, when the braking lever is raised. To raise the lever (against the restoring force of its return spring 103) during the reset cycle, the upper edge of reset slide 136 engages and lifts the right-hand extremity of the brake lever 99, to bring the lever against the cable drum. Since the purpose of this brake is to cut down on any excess wheel excursion at the end of reset, the brake mechanism could be replaced by a fairly "sloppy detent acting on the font wheel in the same manner (i.e., coming into action only at the end of the resetting).

The low-voltage high-current reset pulse applied to magnet 80 pulls in armature 158 quickly, rotating the bellcrank arms 160, 164 and 165 clockwise, and connecting pin 168 moves away from lever 166, the spring 170 being additionally tensioned so as to urge lever 166 upwardly. The lever 166 engages and raises the reset slide 136 (spring 170 being stronger than spring 138, spring 144 and spring 94), resetting all of the unlatched cranks by reason of the engagement of the cam surfaces of the reset notches (such as 134) with the rounded noses described above. This is true as to all of the five upper bellcranks; if the 32-bit crank 120 had been unlatched, it would be restored by the engagement of the tip of lever 166 (at 176) with the lower edge of the crank 120 latching arm. In all cases, the resetting motion allows the crank arms to clear the tips of the respective leaf spring armatures of the selecting magnets 680-681", which tips drop behind the crank arms to restore the condition illustrated in Flg. 3. An eccentrically adjustable back stop is provided for lever 166, as at 178.

The lost-motion connection provided between cranks 164, 165 and lever 166 allows the armature 158 of reset magnet 80 to pull in as quickly as possible when the reset pulse commences, the lever 166 following, under the pressure of tensioned spring 170, at a slower rate determined by the fairly heavy reset load involved in rotating several or even all of the unlatched bellcranks 110 through 120. When the reset pulse ends, the armature 158 is released, and the overtension in spring 170 is released as lever 166 is moved downward by pin 168, as well as by the force provided by the reset slide spring 138.

For use in advancing the impression tape an incremental step following the printing of a character (and, in fact, simultaneously with the reset operation just described), a cable 180 is secured to a pin 182 frictionally secured (for cable-length adjustment) to lever 166. This cable passes around guide pulleys 184 and 186 mounted on plate 86, and thence upward (in FIG. 3) but beneath the type wheel 88, to a guide pulley 188, from which it passes to the right adjacent the back wall 42 of the main casing.

FIG. 3-A of the drawings illustrates in fragmentary form a portion of a modified font wheel 88' in which short radial slots 91 are provided between character configurations (in an otherwise solid font wheel), to prevent any distortion of the wheel rim if the material tends to spread due to the constant peening action of repeated impressions. This figure also shows the shoulder screw 89 which allows easy replacement of one font wheel by another when desired.

The tape feeding arrangement is best shown in FIG. 4, which is a section looking downward at the upper edge of FIG. 3. The cable is seen passing (to the left in this view, of course) around pulley 188 mounted on the right extension of a block 190 forming part of the mechanism plate 86. The cable 180 is secured to the upper arm of a lever 192 pivoted on the block, and urged to the counterclockwise position shown, by spring 194 whose other end is secured to the block by a pin. The other end of lever 192 carries one end of a leaf spring drive element 196 whose left end engages in the teeth of ratchet wheel 198, connected to the frictional tape-drive puck or roller 202. An antirollback pawl 200 also engages the ratchet wheel. A spring 204 connects the drive leaf spring 196 to an anchor pin in the block, to maintain its end engaged with the ratchet wheel teeth, but to allow it to slide idly over the teeth after completion of a feeding step.

Blank tape 10 enters from the right in FIG. 4, along the upper surface of the baseplate 16, and between it and the undersurface of the block 190, which is slotted or relieved to permit this. As it approaches the drive puck 202, the tape passes above a thin sheet metal guide plate 206 anchored in a flush position in the baseplate as by screws 208, this plate curving up and around the drive puck, and in contact therewith along a substantial arc. The tape thus is urged by the arcuate plate surface against the surface of the drive puck, so that when the ratchet wheel 198 is stepped by the pawl 196 (in response to the pull on cable 180 during each reset operation), the tape will be correspondingly advanced.

A bifurcated sheet metal stripping finger plate 210 straddles the width of puck 202 (whose face width may be only a fraction of the tape width) at a point in advance of that at which the tape leaves the puck, so that during threading (as well as thereafter), the tape is constrained to leave the puck along the path defined between the body of this stripping plate and the overlying end of plate 206. The tape is thus so directed as to pass (see FIG. 3) just above the type wheel 88 and between it and the hammer 38, and thence into guide channel 40 (FIGS. 1 and 3). A resilient bumper 212 secured on the underside of keyboard 46 forms a quiet backstop for the hammer arm 152.

It will be noted that the ratchet feed arrangement prevents any backward motion of the tape 10, while it permits the user to withdraw tape as desired by pulling in the forward direction, such as for removal a message strip. In initial threading, the free end of the tape issuing from beneath guide 36 in FIG. 1 is merely pushed into the relieved channel beneath block 190 (FIG. 4) until it is stopped by engaging the part of plate 206 where it meets puck 202. Operation of the keyboard space bar will then advance the tape along the proper path until it emerges, or becomes visible in window 48. A manual tape feed knob may be provided also, if desired.

From the standpoint of the printing mechanism as described, it will be observed that the provision of an extremely light, low-inertia printing font element which lies closely adjacent a rugged and solid backup element, functioning as an anvil, and which font element in effect skims alongside that backup element, allows a very high speed character selecting operation, because the font element does not have to withstand the printing force except in pure compression directly at the type face area. The impression paper (tape) lies between the other face of the font element and the impact means or hammer. This advantage is achieved regardless of whether the impact means or hammer is in front of the tape or behind it (the font wheel and its anvil being on the other side), but for maximum visibility, the arrangement shown herein is preferred.

From the standpoint of the selecting mechanism, which controls the position of the font element, various advantages are obtained, including simplicity, the ability to select any character within a full peripheral font by font rotation of only slightly over a half-tum thereof, and the use of a single power reset magnet. In this connection, the use of individual and relatively low-powered selecting magnets to unlatch the individual bit-selecting devices is also a distinct advantage. These unlatched elements are then restored to latched condition by the single reset magnet operating through a storage spring (170).

lt is to be understood that references to the magnets 68c and 68]" by the designations 16-bit and 32-bit are a reference to their positions in the binary control sequence, and do not necessarily imply that the amount of font wheel rotation which each produces (when it pulls on cable 92) is double the rotation produced when the previous magnet in the series is operated to release the cable. This standard binary nomenclature is adopted for the sake of a quicker understanding on the part of those skilled in the art.

FIG. 6 of the drawings illustrates, in schematic sectional form, a different way in which the principle of maintaining the type font element in very close relation to the anvil or backup member can be realized. In this case, as before, either the font and anvil, as a unit, may be impressed against a relatively fixed platen or impressing member, or the printing may be accomplished by forcing the impression paper against that unit by driving the platen" or a bang bar against the relatively fixed font-and-anvil unit. This FlG. also illustrates the application of the principle in the case of a line-by-line printer having a moving carriage (in contrast to the moving tape of FIGS. 1 and 35).

In FIG. 6, the element bearing the type face configurations is shown as a cup 214 having the tumed-up rim 216 with type faces on the outer rim surface as at 216. A bearing 218 journals the cup on an upstanding stub shaft 220, the cup having a depending bearing sleeve for the purpose. Around and affixed to the bearing sleeve is a pulley or the like 222, to which the selection control cable 92 is connected so that character selection is effected as already described. Stub shaft 220 is secured to a carriage element 224 (where character spacing is to be obtained by a carriage movement) slightly rotatable about, and slidable along, a fixed carriage guide rod 226.

From the upper end of shaft 220, there extends the anvil or backup element 228, welded or otherwise secured to the shaft and terminating, at its left end, just behind the inner surface of the type face cup, the clearance being again just sufficient to allow the type cup to skim past the backup element for character selection purposes. The impression paper is indicated as 230, and the impressing member as a hammer head configuration 232 pivoted on a rod 234 for swinging impressing motion to bring together the paper 230 and the type face which has been selected. This hammer head may be arranged to travel in the direction of moving carriage motion for the successive imprints, or the hammer head configuration may be replaced by a lengthy fixed "bang bar by which impressions may be made at any point along a printed line. Also, as indicated by dash lines at 236, the impressing member may be a conventional round platen.

It is obvious that the bringing together of the impression member, the impression medium or paper, the type face element, and the anvil or backup member, may be accomplished either by swinging the carriage element 224 to the left, or the impression member 232 to the right. Means are illustrated for performing either choice, namely a magnet 238 that can attract a downwardly extending spring-biased tail 240 of the carriage 224, and a magnet 242 that can attract a similar downwardly extending tail 244 of the impression member 232.

In all cases, the low-inertia type face element merely skims along, with minimum rotational clearance, past the anvil 228, which is thus always available for its backing-up function when the impression is to be made.

A wide variety of design choices are available without departing from the basic principle of the closely backed-up, skimming, low-inertia type face element. The angle of upturn of the cup rim in FIG. 6 need not be a full but may for example be 45", to provide a conical configuration, the parts being located to maintain perpendicularity of contact between the type face and the record medium. Any kind of record medium may be employed, either of the pressure-sensitive marking type which requires no marking ribbon, or ordinary aper or tape together with a markingribbon, or by the use of inked type faces. It is immaterial also whether the anvil and printing element together move to make the impression, or the platen or other impression member (hammer, bang-bar) moves toward the type face and anvil unit, so long as the minimum type face-to-anvil clearance is maintained, and there is a rigid impression member on the other side of the impression medium from this unit. Other variants in the designs will occur to those skilled in the art, and it is intended to cover all such which fall within the scope of the appended claims.

I claim:

1. In a character printer having a single-row type wheel mounted for rotation relative to a support, a type wheel position selecting mechanism comprising a single flexible and inextensible cable wrapped about a circular element secured to said type wheel, one end of said cable being resiliently connected to said support, and the other end of said cable passing in a back-and-forth serpentine path over a plurality of coplanar pulleys and its extremity being anchored to said support; respective coplanar spring-pressed levers mounting each of said pulleys for limited motion laterally of said path to alter the effective cable length between said circular element and the anchored end of said cable by predetermined differing amounts, means for latching each of said levers, and thereby each of said pulleys, in its position corresponding to the greater effective cable length, and selectively-operable electromagnets for selectively releasing the latching means of selected ones of said levers.

2. A character printer in accordance with claim 1, including a single movable restoring member cooperating with all of said levers, and a single electromagnet for moving said restoring member and thereby all of said levers which are unlatched, and restoring said pulleys to their latched condition.

3. A character printer in accordance with claim 1, including a further pulley over which said cable passes in a continuation of said serpentine path, means for latching said further pulley in a position corresponding to the lesser effective cable length for that particular pulley, and an electromagnet for selectively releasing the last-named latching means.

4. A character printer in accordance with claim 2, and means controlled by said single electromagnet for advancing impression paper relative to said type wheel.

5. A character printer in accordance with claim 2, including means operated by said single electromagnet for damping the motion of said type wheel to prevent overshoot past a home position thereof. 

1. In a character printer having a single-row type wheel mounted for rotation relative to a support, a type wheel position selecting mechanism comprising a single flexible and inextensible cable wrapped about a circular element secured to said type wheel, one end of said cable being resiliently connected to said support, and the other end of said cable passing in a back-andforth serpentine path over a plurality of coplanar pulleys and its extremity being anchored to said support; respective coplanar spring-pressed levers mounting each of said pulleys for limited motion laterally of said path to alter the effective cable length between said circular element and the anchored end of said cable by predetermined differing amounts, means for latching each of said levers, and thereby each of said pulleys, in its position corresponding to the greater effective cable length, and selectively-operable electromagnets for selectively releasing the latching means of selected ones of said levers.
 2. A character printer in accordance with claim 1, including a single movable restoring member cooperating with all of said levers, and a single electromagnet for moving said restoring member and thereby all of said levers which are unlatched, and restoring said pulleys to their latched condition.
 3. A character printer in accordance with claim 1, including a further pulley over which said cable passes in a continuation of said serpentine path, means for latching said further pulley in a position corresponding to the lesser effective cable length for that particular pulley, and an electromagnet for selectively releasing the last-named latching means.
 4. A character printer in accordance with claim 2, and means controlled by said single electromagnet for advancing impression paper relative to said type wheel.
 5. A character printer in accordance with claim 2, including means operated by said single electromagnet for damping the motion of said type wheel to prevent overshoot past a ''''home'''' position thereof. 